Re: [PATCH 0/3] make pfn walker support ZONE_DEVICE

[Toshiki Fukasawa]

On 2019/11/08 18:18, Michal Hocko wrote:
> On Fri 08-11-19 00:08:03, Toshiki Fukasawa wrote:
>> This patch set tries to make pfn walker support ZONE_DEVICE.
>> This idea is from the TODO in below patch:
>>
>>    commit aad5f69bc161af489dbb5934868bd347282f0764
>>    Author: David Hildenbrand <david@xxxxxxxxxx>
>>    Date:   Fri Oct 18 20:19:20 2019 -0700
>>
>> 	fs/proc/page.c: don't access uninitialized memmaps in fs/proc/page.c
>>
>> pfn walker's ZONE_DEVICE support requires capability to identify
>> that a memmap has been initialized. The uninitialized cases are
>> as follows:
>>
>> 	a) pages reserved for ZONE_DEVICE driver
>> 	b) pages currently initializing
>>
>> This patch set solves both of them.
> 
> Why do we want this? What is the usecase?

We are writing a test program for hwpoison, which is a use case.
Without this patch, we can't see the HWPOISON flag on the
ZONE_DEVICE page.

Thanks,
Toshiki Fukasawa